1. Field of the Invention
The present invention relates generally to wire cable ducts.
2. Description of the Prior Art
Prior art wire cable ducts take the form of a grid made up of wires of two different types, namely longitudinal wires, usually referred to as warp wires, which run longitudinally the entire length of the duct in a rectilinear or quasi-rectilinear manner and, disposed transversely to the longitudinal wires, from place to place along their length and appropriately attached thereto, U-shaped transverse wires, usually referred to as weft wires, the combination forming three panels which in practice are planar or substantially planar, namely a bottom panel and two side panels, usually referred to as flanges.
They are routinely used as troughs to support, house and protect electrical cables or the like.
Here and hereinafter the expression xe2x80x9celectrical cablesxe2x80x9d refers not only to cables adapted to convey and distribute electrical energy but also to cables and fibers adapted to transmit information in electrical, optical or other form.
With regard to electrical cables, wire cable ducts have many advantages which are appreciated by electrical installers and in particular the advantages of easy installation, and therefore economy, flexibility, because the electrical cables can exit through any mesh of the grid, transparency, and therefore of easy identification of the electrical cables, ventilation, cleanliness, safety, both with regard to the electrical cables themselves and users, and performance.
By virtue of their very design, the maximum span of the above wire cable ducts is limited, as are the loads they are able to support: for this reason the inherent capacity of the trough shape is not completely utilized, unless the number of supports and jointing members is increased, which is to the detriment of assembly time and therefore to installation cost; also, the installation environment often rules out the fitting of numerous supports.
The side panels comprise a longitudinal row of successive substantially rectangular and plane edge meshes which constitute the upper part of the side panels and each of which is defined between the facing flange portions of two consecutive U-shaped transverse wires and between two longitudinal wires which cross over them. They sag to a non-negligible degree when heavily loaded.
An object of the present invention is to avoid the above drawbacks and to propose a wire cable duct with a longer span or higher loading capacity than prior art wire cable ducts; thus the present invention provides a high-strength cable duct.
The document FR-A-2 706 973 describes a cable duct of the above kind which is made stronger by fixing reinforcing lateral spars to the side walls of a wire trough which overlie the side walls completely.
Numerous trials carried out by the inventors of the present invention have shown that, in order to increase the stiffness of a meshed cable duct, it is sufficient to limit flexing of only the edge meshes, which is a simpler and less costly solution than that disclosed by the above prior art document.
Accordingly, the invention provides a wire cable duct comprising a grid made up of wires of two different types, namely at least one longitudinal wire which runs longitudinally the entire length of the duct and U-shaped transverse wires disposed transversely to the longitudinal wires, from place to place along their length and appropriately attached thereto, the resulting trough-like combination forming three panels, namely a bottom panel and two side panels, which side panels comprise a longitudinal row of successive plane and substantially rectangular edge meshes which constitute upper parts of the side panels, each of which is defined between two facing flange portions of two consecutive transverse wires, and each of which includes at least one anti-flexing member adapted to limit its flexing about an axis perpendicular to its plane.
In a first embodiment each edge mesh consists of two longitudinal wires joined to facing flange portions of two transverse wires and to each other by at least one crossmember. The crossmember is parallel to the flange portions of the transverse wires. Alternatively, the crossmember is inclined to the flange portions of the transverse wires. In another embodiment the crossmember has an open U-shape with a core attached to one longitudinal wire and arms attached at their ends to the other longitudinal wire. The ends of the arms are preferably also joined to the flange portions of the transverse wires at the intersection thereof with the other longitudinal wire. The core of the open U-shape is advantageously attached to an upper longitudinal edge wire. The crossmember is preferably a continuous wire which is adapted to limit flexing of consecutive meshes and is alternately connected to each of the longitudinal wires delimiting the meshes.
In another embodiment each edge mesh consists of a section attached to the flange portions of the transverse wires. The section is plane and attached to the outside and/or to the inside of the cable duct. Alternatively, the section has an L-shaped cross section defining a longitudinal rim. The section is attached to the outside or to the inside of the cable duct with its longitudinal rim overlying free ends of the flange portions of the transverse wires. The section is attached to the outside of the cable duct with its longitudinal rim directed outward. Thus in these embodiments the edge mesh does not include any longitudinal wires.
In another embodiment the section has a U-shaped cross section with wide flanges and straddles the flange portions of the transverse wires.
In another embodiment the section has a U-shaped cross section with narrow flanges and is attached to the outside of the cable duct with its flanges directed outward. The narrow flanges are straight or have a rolled edge.
The features and advantages of the invention will emerge further from the following description, which is given by way of example and with reference to the accompanying diagrammatic drawings.